1. Field of the Invention
The invention relates to an information processing apparatus using a technique of a scanning tunnel microscope or the like.
2. Related Background Art
In recent years, memory materials are mainly used in the electronics industries such as computer, its peripheral apparatuses, video disc, digital audio disc, and the like. The development of the memory materials is also actively progressing. Although the performances which are required for such memory materials are different depending on the application, it is indispensable that a response speed for recording and reproducing is high.
Hitherto, a semiconductor memory or a magnetic memory which is made of a material such as magnetic material or semiconductor is a main stream. However, in association with the development of the recent laser technique, a cheap recording medium of high density by an optical memory using an organic thin film such as organic pigment, photo polymer, or the like has been put into practical use.
On the other hand, in recent years, a scanning tunnel microscope (hereinafter, abbreviated to STM) which can directly observe an electron structure of a surface atom of a conductor has been developed (G. Binnig, et al., Phys. Rev. Lett, 49, 57, 1982). A real spatial image can be measured at a high resolution irrespective of a difference between a monocrystal and an amorphous material. Moreover, there is also an advantage such that the image can be measured with low electric power without damaging a sample by a current. Further, the STM can operate even in the atmosphere and can be used for various materials. Therefore, applications of a wide range are expected.
The STM uses a principle such that when a voltage is applied between a metal probe (probe electrode) and a conductive material and the probe is allowed to approach up to a distance of about 1 nm, a tunnel current flows. The tunnel current is very sensitive because it exponentially responds to a change in distance between the probe and the conductive material. By scanning the probe so as to keep the tunnel current constant, various information regarding the whole electron cloud in the real space can be also read. In this instance, a resolution in the in-plane direction is equal to about 0.1 nm.
Therefore, by applying the principle of the STM, high density recording and reproduction can be executed with a resolution on the order of atom (subnanometer). For instance, according to an information processing apparatus disclosed in JP-A-61-80536, atomic particles adsorbed on the medium surface are removed by an electron beam or the like and data is written and the written data is reproduced by the STM.
There has also been proposed a method of performing the recording and reproduction by the STM by using a thin film as a recording layer which is made of a material having a memory effect to switch characteristics of a voltage/current, for instance, an organic compound or chalcogen compound class having a conjugate .pi. electron system (JP-A-63-161552, JP-A-63-161553). According to the above method, by setting a pit size for recording to 10 nm, the recording and reproduction of a large capacity of 10.sup.12 bits/cm.sup.2 can be performed.
As a scanning mechanism of the probe electrode, there is a cantilever type (JP-A-62-281138). It is possible to form several tens of cantilever type mechanisms each of which is made of SiO.sub.2 and has dimensions such that a length is equal to 100 .mu.m, a width lies within a range from 10 to 20 .mu.m, and a thickness is equal to 0.5 .mu.m onto an Si substrate. A writing/reading circuit is also integrated on the same substrate.
Generally, in the case of recording and reproducing image information at a high quality, a searching operation such as to pick up an arbitrary one of a plurality of images is required. In case of information such as a still image file in which there is no correlation among the images, such a searching operation is particularly required. Actually, operations such that a plurality of images are simultaneously generated on a display such as a monitor or the like and the operator selects a desired image or the like are executed as such a searching operation. In this case, since an information amount per picture plane is very large, all of the pixels are not generated but they are thinned out and displayed in accordance with the resolution of the monitor. In case of generating the pixels for an apparatus such as monitor, printer, or the like having different display resolutions, the operations such that the pixels are also thinned out and the like are executed and the resultant image data is generated.
Hitherto, however, an image of a low resolution is formed from an original image by software processes. Consequently, it takes a time to form an image of a necessary resolution and output time increases.